CN106989032B - Oblique flow-centrifugal combined compressor - Google Patents

Oblique flow-centrifugal combined compressor Download PDF

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CN106989032B
CN106989032B CN201710147005.0A CN201710147005A CN106989032B CN 106989032 B CN106989032 B CN 106989032B CN 201710147005 A CN201710147005 A CN 201710147005A CN 106989032 B CN106989032 B CN 106989032B
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compressor
centrifugal
flow
centrifugal compressor
stage
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CN106989032A (en
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黄孟璇
王英锋
潘奕君
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04DNON-POSITIVE-DISPLACEMENT PUMPS
    • F04D17/00Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D17/08Centrifugal pumps
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04DNON-POSITIVE-DISPLACEMENT PUMPS
    • F04D23/00Other rotary non-positive-displacement pumps
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04DNON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00Details, component parts, or accessories
    • F04D29/40Casings; Connections of working fluid
    • F04D29/42Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/44Fluid-guiding means, e.g. diffusers
    • F04D29/441Fluid-guiding means, e.g. diffusers especially adapted for elastic fluid pumps

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)

Abstract

The invention discloses a diagonal flow-centrifugal combined compressor, which comprises a diagonal flow compressor, a centrifugal compressor and a vaneless diffuser; the air inlet of the centrifugal compressor and the air outlet of the oblique flow compressor are identical in shape and size, gaps are reserved in mutual fit, and the width of each gap is a preset width threshold value; the axial line of the centrifugal compressor and the axial line of the diagonal flow compressor are on the same axial line; the air inlet of the vaneless diffuser is fixedly connected with the air outlet of the centrifugal compressor; the pressure ratio of the diagonal flow compressor is 2.3 to 2.6, the pressure ratio of the centrifugal compressor is 1.8 to 2, the structure of the invention is compact, the number of parts is small, the reliability is high, and the pressure ratio, the efficiency and the flow performance parameter indexes are all improved by changing the rim speed of the first stage and the second stage.

Description

Oblique flow-centrifugal combined compressor
Technical Field
The invention relates to an impeller mechanical device, in particular to a diagonal flow-centrifugal combined compressor.
Background
As one of the main components of a micro turbine engine, the compressor plays a very important role, "compared with an axial-flow compressor, a centrifugal or diagonal-flow compressor has the advantages of high single-stage supercharging ratio, simple structure, large stable working range, small length, low manufacturing cost and the like.
At present, research in the field of micro turbojet engines at home and abroad mainly focuses on the aspect of optimal design of parts including single-stage centrifugal compressor parts so as to improve the performance of the engine. However, the speed of the blade tip rim of the compressor is improved to a limited extent, and the performance of the engine is difficult to be greatly improved. Particularly, in the aspect of centrifugal compressors, it is imperative to improve the design method thereof to improve the performance of the centrifugal compressor, thereby effectively improving the overall performance of the engine.
Because the flow of the micro turbine engine is small, a single-stage centrifugal compressor is mostly adopted to avoid the phenomenon that the loss of the last stage of the pure axial flow compressor is increased due to the scale reduction effect. With the increasing demand for high performance microturbine engines, there is an inevitable trend to improve compressor pressure ratio and efficiency. However, because the blade root stress of the centrifugal compressor is limited by the stress level of materials, the improvement range of the single-stage pressure ratio is limited, and the maximum blade tip tangential speed is about 600m/s at present. In a turbine engine with a small thrust and power, it has been difficult to increase the pressure ratio by increasing the number of stages due to the restriction of the size of the flow path.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a diagonal flow-centrifugal combined compressor aiming at the defects related in the background technology, wherein a two-stage compressor is adopted, and the pressure ratio, the efficiency and the flow performance parameter indexes are all improved by changing the rim speeds of a first stage and a second stage.
The invention adopts the following technical scheme for solving the technical problems:
a combined oblique flow-centrifugal compressor comprises an oblique flow compressor, a centrifugal compressor and a vaneless diffuser;
the air inlet of the centrifugal compressor and the air outlet of the oblique flow compressor are identical in shape and size, a gap is reserved between the air inlet of the centrifugal compressor and the air outlet of the oblique flow compressor in a mutual fit mode, and the width of the gap is a preset width threshold value;
the axial line of the centrifugal compressor and the axial line of the diagonal flow compressor are on the same axial line;
the air inlet of the vaneless diffuser is fixedly connected with the air outlet of the centrifugal compressor;
the pressure ratio of the diagonal-flow compressor is 2.3 to 2.6, and the pressure ratio of the centrifugal compressor is 1.8 to 2.
As a further optimization scheme of the oblique flow-centrifugal combined compressor, the preset width threshold value ranges from 5mm to 10mm.
Compared with the prior art, the technical scheme adopted by the invention has the following technical effects:
1. when the speed u1 of the outlet blade tip of the front-stage compressor is increased, the total added work amount of the compressor is increased, and the pressure ratio of the compressor is increased according to the relation between the pressure ratio and the work; when u1 is increased, if the total power adding amount of the gas compressor is kept unchanged, the speed u2 of the blade tip at the outlet of the gas compressor at the later stage is reduced, so that the absolute speed radial speed of the outlet gas flow is increased, the loss of a diffuser is reduced, and the overall efficiency of the gas compressor is improved, namely if the power adding amounts of the first stage and the second stage are properly matched, the efficiency and the pressure ratio of the whole stage can be increased;
2. when the scheme of the oblique flow-centrifugal combined compressor is adopted, compared with a single-stage centrifugal compressor, the airflow turning angle and the pressurization born by the original single blade cascade are divided into two blade rows, the development of the thickness of the boundary layer on the surface of each blade is slowed down, and the pneumatic loss is small;
3. as the work load of the first stage of the combined oblique flow and centrifugal compressor is increased, compared with a single-stage centrifugal compressor, the speed of the outlet rim of the first stage is higher than that of the rim of the first stage at the same geometric radius, and the flow capacity of the whole channel is enhanced.
Drawings
FIG. 1 is a side view of a combined diagonal flow-centrifugal compressor according to the present invention;
FIG. 2 is a front view of the combined diagonal flow-centrifugal compressor of the present invention;
FIG. 3 is a graph showing the flow-pressure ratio characteristics of a Krain impeller and an oblique flow-centrifugal combined compressor of the present invention;
FIG. 4 is a graph of the flow-stage efficiency characteristics of a Krain impeller and a mixed flow-centrifugal compressor of the present invention.
In the figure, 1 is an air inlet of a diagonal flow compressor, 2 is the diagonal flow compressor, 3 is the centrifugal compressor, and 4 is a vaneless diffuser.
Detailed Description
The technical scheme of the invention is further explained in detail by combining the drawings as follows:
as shown in fig. 1, the invention discloses a mixed flow-centrifugal combined compressor, which comprises a mixed flow compressor, a centrifugal compressor and a vaneless diffuser;
the air inlet of the centrifugal compressor and the air outlet of the oblique flow compressor are identical in shape and size, a gap is reserved between the air inlet of the centrifugal compressor and the air outlet of the oblique flow compressor in a mutual fit mode, and the width of the gap is a preset width threshold value;
the axial line of the centrifugal compressor and the axial line of the oblique flow compressor are on the same axial line;
the air inlet of the vaneless diffuser is fixedly connected with the air outlet of the centrifugal compressor;
the pressure ratio of the oblique-flow compressor is 2.3 to 2.6, and the pressure ratio of the centrifugal compressor is 1.8 to 2.
In the invention, the first stage is a diagonal flow compressor, the second stage is a centrifugal compressor, the airflow sequentially passes through the diagonal flow compressor, the centrifugal compressor and the vaneless diffuser, and the range of the preset width threshold value is 5-10 mm, so that the loss of the wake caused by the clearance is reduced to the minimum.
When the centrifugal compressor is used, the diagonal flow compressor is connected with the first turbine through the first shaft, the centrifugal compressor is connected with the second turbine through the second shaft, and the first shaft and the second shaft are coaxially sleeved. The rotating speed of the low-pressure turbine is higher than that of the high-pressure turbine during working, and work output of the low-pressure turbine is improved.
The invention improves the pressure ratio, efficiency and flow performance parameters at the same time by changing the rim speeds of the first stage and the second stage.
FIG. 2 is a front view of the combined diagonal flow-centrifugal compressor of the present invention, in which the central circle is the inlet of the diagonal flow compressor, the middle ring is a first cross-section, and the outer ring is a second cross-section, so that the work per unit flow of gas is L when only a single-stage centrifugal compressor is used c =C 2u ×U 2 In the formula, C 2u Absolute velocity C of point B 2 Of the tangential component of the impeller, U 2 The rim speed of the impeller at point B, the first section adding amount is L c1 =C 1u ×U 1 ,C 1u Absolute velocity C at point A 1 Of the tangential component of the impeller, U 1 The rim speed of the impeller at the point A, and the adding amount of the work from the first section to the second section is L c2 =C 2u ×U 2 -C 1u ×U 1 (ii) a When the combined oblique flow-centrifugal compressor is adopted, the first section work adding amount is L c1 =C 1u ×U 1 The work addition from the first section to the second section is L c2 '=C' 2u ×U' 2 -C 1u ×U 1 ',C' 2u Is absolute speed C 'of point B' 2 Of the impeller tangential component, U' 2 Rim speed of impeller at point B', U 1 ' is a centrifugal impellerRim velocity at the inlet of the second section, so the total work addition L = C 'of the combined oblique flow-centrifugal compressor at this time' 2u ×U' 2 -C 1u ×(U 1 '-U 1 ). When the speed u1 of the outlet blade tip of the front-stage compressor is increased, the total added work amount of the compressor is increased, and the pressure ratio of the compressor is increased according to the relation between the pressure ratio and the work; when u1 is increased, if the total work adding amount of the compressor is kept unchanged, the speed u2 of the blade tip at the outlet of the compressor at the rear stage is reduced, the absolute speed radial speed of the airflow at the outlet is increased, the loss of a diffuser is reduced, and the overall efficiency of the compressor is improved.
The technical scheme and the full three-dimensional numerical method are verified, and the Krain high subsonic speed centrifugal impeller with detailed blade profile data and experimental data is adopted in verification.
The Krain impeller is a semi-open impeller which is designed by Krain doctor of Germany space institute and has a back bend angle (included angle between blades and tangential direction) of 60 degrees, a design flow rate of 4.0kg/s, a rotating speed of 22363r/min, a blade number of 24, a blade tip linear speed of 470m/s and an impeller pressure ratio of 4.7, the efficiency of the impeller design point is about 93 percent, the pressure ratio of the whole stage is 4, and the efficiency is 82.51 percent. The impeller can work efficiently in a very wide flow range through experimental tests, meanwhile, the impeller has detailed blade profile data and experimental measurement results, and many scholars at home and abroad adopt the impeller as a research object.
The Krain high subsonic speed centrifugal impeller is divided into two stages, the backward bending angle (included angle between blades and tangential direction) of the two stages is 60 degrees, the flow rate of a design point is 51.8kg/s, the first stage rotating speed is 2450 r/min, the number of the blades is 24, the first stage blade tip speed is 384.5m/s, the second stage rotating speed is 21500r/min, the second stage blade tip speed is 450.3m/s, the impeller pressure ratio is a semi-open impeller of 4.74, the impeller design point efficiency is about 92 percent, the pressure ratio of the whole stage is 4.5, and the efficiency is 86.26 percent. The two are the same in geometric dimension, and a flow-pressure ratio characteristic curve and a flow-stage efficiency characteristic curve of the Krain impeller and the mixed-flow-centrifugal compressor are respectively shown in the figures 3 and 4.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (2)

1. A diagonal flow-centrifugal combined compressor is characterized by comprising a diagonal flow compressor, a centrifugal compressor and a vaneless diffuser;
the shape and the size of the air inlet of the centrifugal compressor and the shape and the size of the air outlet of the oblique flow compressor are the same, a gap is reserved between the air inlet of the centrifugal compressor and the air outlet of the oblique flow compressor in a mutual fit mode, and the width of the gap is a preset width threshold value;
the axial line of the centrifugal compressor and the axial line of the oblique flow compressor are on the same axial line;
the air inlet of the vaneless diffuser is fixedly connected with the air outlet of the centrifugal compressor;
the pressure ratio of the oblique-flow compressor is 2.3 to 2.6, and the pressure ratio of the centrifugal compressor is 1.8 to 2.
2. The combined slipstream-centrifugal compressor according to claim 1, characterized in that said preset width threshold ranges from 5mm to 10mm.
CN201710147005.0A 2017-03-13 2017-03-13 Oblique flow-centrifugal combined compressor Active CN106989032B (en)

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CN116753190B (en) * 2023-08-23 2024-03-22 江苏乐科节能科技股份有限公司 Tandem centrifugal compressor impeller with middle static blade grid

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB191027525A (en) * 1910-11-26 1911-11-09 Wilfred Hunt An Exhauster or Compressor for Gases also applicable as an Ejector-condenser.
CA2658412A1 (en) * 2009-03-16 2010-09-16 Pratt & Whitney Canada Corp. Hybrid compressor
KR20110125717A (en) * 2010-05-14 2011-11-22 국방과학연구소 Mixed-flow type compressor
CN102678590A (en) * 2011-03-07 2012-09-19 中国科学院工程热物理研究所 Ultra-compact high-pressure ratio oblique flow-centrifuge combined compressor structure
CN104895841A (en) * 2015-04-30 2015-09-09 中国科学院工程热物理研究所 Rectifier, runner structure, combined gas compressor and aviation gas turbine engine
CN105257574A (en) * 2015-11-27 2016-01-20 中国航空动力机械研究所 Oblique flow and centrifugal combined compressor
CN206668584U (en) * 2017-03-13 2017-11-24 南京航空航天大学 A kind of Novel inclined is wandered about as a refugee heart combined compressor

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB191027525A (en) * 1910-11-26 1911-11-09 Wilfred Hunt An Exhauster or Compressor for Gases also applicable as an Ejector-condenser.
CA2658412A1 (en) * 2009-03-16 2010-09-16 Pratt & Whitney Canada Corp. Hybrid compressor
KR20110125717A (en) * 2010-05-14 2011-11-22 국방과학연구소 Mixed-flow type compressor
CN102678590A (en) * 2011-03-07 2012-09-19 中国科学院工程热物理研究所 Ultra-compact high-pressure ratio oblique flow-centrifuge combined compressor structure
CN104895841A (en) * 2015-04-30 2015-09-09 中国科学院工程热物理研究所 Rectifier, runner structure, combined gas compressor and aviation gas turbine engine
CN105257574A (en) * 2015-11-27 2016-01-20 中国航空动力机械研究所 Oblique flow and centrifugal combined compressor
CN206668584U (en) * 2017-03-13 2017-11-24 南京航空航天大学 A kind of Novel inclined is wandered about as a refugee heart combined compressor

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